The present invention is generally related to the transfer of images in both wet and dry type of image processing systems which utilize a recording member, such as a photoconductor, and toner particles for developing an image thereon.
The invention is particularly applicable to an addressing device for objects of varying physical characteristics and having some degree of transfer surface conductivity to receive the particle pattern. The invention will, therefore, be described with respect to this addressing purpose, although it will be appreciated that the invention has broader applications such as where voluminous objects of uniform characteristics, such as a stack of cards, are to receive image patterns transferred to their respective surfaces.
In the past, conventional techniques of developed image transfer have, for the most part, proven unsatisfactory, due in part to the physical properties of the transfer member and the environmental variables in which the transfer is performed. Factors such as temperature, pressure, and humidity can adversely affect the electrical characteristics of the transfer member, thereby causing a poor quality of transfer. Environmental variables are critical due in part to the fact that the transfer object acts as a capacitive storage medium during transfer. This is recognized in U.S. Pat. No. 2,807,233 to Fitsch, which mentions that a condenser is formed at the transfer station with the transfer web (object) serving as one of the dielectrics.
Each of the conventional transfer techniques required the use of an electrode, or the like, positioned behind the transfer member, such that the transfer member is sandwiched between the electrode and the insulating layer. Typically, the electrode takes the form of a roller, cylinder, plate, wire, or brush. High voltage is applied to the electrode to set up an electrical field through the transfer member, utilizing the electrostatic storage capacity of the transfer member to effect transfer of the toner particles.
Since such conventional transfer devices have required the use of a backup electrode, they are incapable of transferring a developed image to bulky or nonuniform items, such as boxes, magazines, and cartons. It is also apparent that such conventional devices are unable to effect transfer to the top or bottom sheet of a stack of paper, or the like, so as it would be impractical or impossible to position the electrode behind the respective sheet to which transfer is to be made.
The present invention provides a new and improved method and apparatus which overcomes all of the above referenced problems and provides a method of developed image transfer for bulky and nonuniform objects, as well as for stacks of uniform items, without the need for electrode backing and functionally independent of the bulk characteristics of the transfer object, in a manner which is simple, efficient and assures a perfect transfer.